Thanks guys for your input. I will give up implementing backup and Verify in parallel. Instead, I will implement backup and restore(in other machine) in parallel. 

It makes to think about another question. Why do we backup? The short answer is for restore. But when? Actually, disaster is a very small probability event. In most cases, we do that for new environment initialization or data migration. The tradition process is, to backup DB to local disk or share, then copy backup to target server, and then restore it. There are two problems.
(1) We can't restore until Backup is 100% finished.
(2) Extra storage is needed. 

With backup and restore in parallel, Backup DB in Instance-A, and directly restore it in Instance-B at the same time, even though one or both of them stand in AWS EC2. No storage & No Wait! Sounds good?